NOx removing pavement structure

ABSTRACT

The NO x -cleaning paving structure of the present invention comprises a concrete base layer  1 , a paving layer  2  and a surface layer  3  as illustrated in FIG.  1 . The surface layer  3  comprises 100 parts by weight of cement, 5-50 parts by weight of titanium oxide powder and 100-700 parts by weight of aggregate, by which the surface layer on the paving layer can be provided with an NO x -cleaning action and an excellent durability. In addition, pozzolan materials, particularly a blast furnace slag, or adsorbing materials can be added to the surface layer. The paving layer  2  comprises an asphalt paving  21  or a concrete paving  6 , both of which may include the used paving layers. It is preferable that the asphalt paving is porous and the surface thereof has an unevenness. Additionally, it is preferable that the thickness of the surface layer is 1-300 mm for the concrete paving and 2-15 mm for the asphalt paving. Among cement, injection cement for half-flexible paving is preferable.

TECHNICAL FIELD

The present invention relates to an NO_(x)-cleaning paving structure,and more particularly to an NO_(x)-cleaning paving structure in which aNO_(x)-cleaning action and an excellent durability are provided to thesurface layer of a paving layer or a surface layer constructed byOverlay method for a paving layer.

BACKGROUND ART

NO_(x) is present in exhaust gas discharged from automobiles,particularly diesel motorcars. Air pollution caused by NO_(x) hasincreased because of the increasing number of automobiles in use,because of increased traffic congestion, and the like.

Known NO_(x) concentration-lowering materials include metal oxides, ofwhich titanium oxide, more particularly titanium dioxide is known tohave a strong photocatalytic action.

Research into removing NO_(x) by the strong photocatalytic action hasbeen more active nowadays. For example, the removal of NO_(x) by usingthe external walls of buildings constructed of sheets or panels whichincorporate titanium dioxide therein is nearing the commercial stage.

Under the above-mentioned situation, the present inventors have filedthe patent applications of HEI 8-38137, HEI 8-58945, HEI 8-113507 andHEI 8-126659 relating to NO_(x)-cleaning materials having titanium oxidein cement from the standpoint that a chemical stability is required formaterials by which titanium oxide is held since titanium dioxide has astrong photoactivity.

The present inventors have now found that the following advantages canbe obtained when NO_(x)-cleaning materials are used as a surface layerprovided to a road surface.

(1) The surface of road has many chances to be attacked by sunlight andrain as the surface thereof is flat with result that great effects areobtained for cleaning capability and refreshing.

(2) Paving layers can be simultaneously exchanged as a public officecontrols roads.

(3) As distances between roads and automobiles are short, an efficiencyof contact with an exhausting gas including NO_(x) is high.

Though there was proposed a plan of holding titanium oxide in asphalt incase of asphalt paving of paved roads, the asphalt used for generalroads has a defect of deterioration cased by the photocatalytic actionas well as a defect of a low NO_(x)-cleaning capability.

In case of concrete paving, though can be made an NO_(x)-cleaningstructure having titanium oxide in the whole of the concrete, a largequantity of expensive titanium oxide is used, which is economicallyundesirable.

Considering the above-mentioned situation, in the former case of asphaltpaving, the present inventors have found that a paved road withoutdeterioration of asphalt and having an excellent durability can beobtained by providing an asphalt surface with a dough of cement andtitanium oxide added thereinto, not by adding directly titanium oxide toasphalt to hold the titanium oxide in the asphalt and have found that byadopting porous asphalt, NO_(x)-cleaning materials are penetrated intopores of porous asphalt with the result that an increased durability canbe obtained.

In the latter case of concrete paving, the inventors have found that theexpensive titanium oxide can be efficiently used either by providing asurface layer including titanium oxide on the concrete paving or byproviding a surface layer including titanium oxide on a used concretepaving arranged by concrete overlay method.

The present invention has been carried out, based on the above-mentionedfindings.

Accordingly, one object of the present invention is to provide anNO_(x)-cleaning paving structure having a surface layer on a pavinglayer which is excellent in an NO_(x)-cleaning action and durability.

Another object of the present invention is to provide an NO_(x)-cleaningpaving structure having a surface layer which is provided on a pavinglayer by overlay method and excellent in an NO_(x)-cleaning action anddurability.

DESCRIPTION OF THE INVENTION

The above-mentioned objects of the present invention are achieved byeach of the following inventions (1) to (16).

Throughout the specification and the claims, the term “for pavingpurposes” includes within its scope the “paving sideways or roadways”.The NO_(x)-cleaning paving structure of the present invention isprovided with the following excellent effects.

(1) The basic NO_(x)-cleaning paving structure of the present inventioncomprises a paving layer and a surface layer in order, the surface layerbeing obtained from 100 parts by weight of cement, 5-50 parts by weightof titanium oxide powder, 100-700 parts by weight of aggregate and 5-100parts by weight of water. As the surface layer contains both cement andtitanium oxide, the paving having an NO_(x)-cleaning capability and anexcellent durability is available.

(2) In the invention described in the above-mentioned (1), by adoptingthe paving layer composed of asphalt paving, the surface layer includingtitanium oxide is provided on the asphalt layer with the result that theasphalt layer is not deteriorated by titanium oxide, and as the surfacelayer contains cement, the surface layer is excellent in durability.

(3) In the invention described in the above-mentioned (1), titaniumoxide can be contained only in the surface layer by adopting the pavinglayer composed of concrete paving, thereby to use expensive titaniumoxide efficiently. Furthermore as the structure has the surface layercontaining cement on the concrete paving, the concrete paving and thesurface layer are strongly adhered each other, thereby to form pavinghaving an enhanced durability.

(4) In the invention described in the above-mentioned (1), by adoptingthe paving layer composed of a part of used asphalt paving, there areavailable the effects of the present invention described in theabove-mentioned (2) as well as it is not necessary to form again thepaving from the beginning as the surface of the used asphalt paving isshaved off by overlay method and the surface including cement andtitanium oxide is formed on the shaved part.

Accordingly excellent effects can be gained in the points that the termof work is shortened and the cost becomes small.

(5) In the invention described in the above-mentioned (1), by adoptingthe paving layer composed of a part of concrete paving, there areavailable the effects of the present invention described in theabove-mentioned (3) as well as it is not necessary to form again thepaving from the beginning as the surface of the used concrete paving isshaved off by well-known concrete overlay method and the surface layerincluding cement and titanium oxide is formed on the shaved part.

Accordingly excellent effects can be gained in the points that the termof work is shortened and the cost becomes small.

It goes without saying that the surface properties of the used pavinglayer can be recovered and the structure thereof can be strengthened.

(6) In the invention described in any of the above-mentioned (1) to (5),sunlight penetration is possible by limiting the thickness of thesurface layer to from 1 to 300 mm and the catalytic reaction of titaniumoxide can be performed efficiently.

(7) In the invention described in any of the above-mentioned (1) to (6),the work can be carried out efficiently by forming the surface layerusing a dough including a high-performance reduction-water agent as thefluidity of the dough is improved in the work.

(8) In the invention described in any of the above-mentioned (1) to (7),the bending property and strength of the surface layer are afforded byforming the surface layer having 0.1 to 50 parts by weight of fiber,with the result that the enhanced durability of the paving is available.

(9) In the invention described in any of the above-mentioned (2), (4) or(6) to (8), a strong base layer for the asphalt layer is available byproviding the asphalt layer with the base layer made of concrete, withthe result that the paved road excellent in durability is available.

(10) In the invention described in any one of the above-mentioned (2),(4) or (6) to (8), a strong base layer for the asphalt layer isavailable by providing the asphalt layer with the base layer comprisinga rock bed, with the result that the paved road excellent in durabilityis available.

(11) In the invention described in any of the above-mentioned (2), (4)or (6) to (8), the paving work cost is small and the work can be carriedout efficiently by forming the base layer for asphalt comprising atleast one selected from soil, macadam and stone, and the paved roadformed has an NO_(x)-cleaning capability corresponding to that of thepaved road having the concrete base layer.

(12) In the invention described in any of the above-mentioned (2), (4)or (6) to (8), a part of the surface layer is penetrated into pores of aporous asphalt layer in the paving work by providing the asphalt layerwhich is porous, with the result that the surface layer and the asphaltlayer are strongly adhered each other and the paving excellent indurability is available.

(13) In the invention described in any of the above-mentioned (1) to(12), the surface layer is strongly adhered by proving the surface ofthe paving layer with an unevenness with the result that the surfacelayer is excellent in durability, by which excellent effects areobtained for the paving of roadways.

(14) In the invention described in any one of the above-mentioned (1) to(13), the surface layer is enhanced in strength and a water seal thereofis increased by adding 10-50% by weight of an admixing additivecomprising a pozzolan material relative to cement to form the surfacelayer with the result that the surface layer is enhanced in durabilityand in addition, there are available excellent effects such as strongresistance to an acid circumstance.

(15) In the invention described in any of the above-mentioned (1) to(13), a hydrant reaction is made dull by adding 10-50% by weight of anadmixing additive comprising a blast furnace slag having a powder valueless than 4000 m²/g relative to cement to form the surface layer.

(16) In the invention described in any of the above-mentioned (1) to(15), by adding 2-30% by weight of an adsorbing material relative tocement to form the surface layer, the following excellent effects areavailable: NO_(x) is decomposed and removed by sunlight ofdays(ultraviolet rays included in sunlight) as well as NO_(x) isadsorbed by the adsorbing material during nights and is decomposed byultraviolet rays with the result of removing NO_(x).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an NO_(x)-cleaning paving structureof asphalt of the present invention.

FIG. 2 is a cross-sectional view of another NO_(x)-cleaning pavingstructure of the present invention.

FIG. 3 is a cross-sectional view of still another NO_(x)-cleaning pavingstructure of the present invention.

BEST MODES OF PRACTICING THE INVENTION

While the embodiments of the present invention are described belowfurther in detail showing examples, the present invention is not limitedto the described embodiments.

The NO_(x)-cleaning paving structure of the present invention ischaracterized by comprising in order a paving layer and a surface layerwhich is obtained from 100 parts by weight of cement, 5-50 parts byweight of titanium oxide powder, 100-700 parts by weight of aggregateand 5-100 parts by weight of water.

The paving layer includes asphalt paving and concrete paving. Theasphalt paving is formed by known construction methods of asphalt roads.

As the examples of forming the asphalt roads, there is a method offorming the asphalt layer of the present invention on a concrete baselayer, anther method of providing a styrofoam layer and forming theasphalt layer of the present invention on the styrofoam layer, stillanother method of forming directly the asphalt layer of the presentinvention on the worked surface of a road, namely the worked soilsurface which is a base layer, still another method of forming theasphalt layer of the present invention on gravel, stone or the like laidas a base layer. The above-mentioned methods of forming the asphaltroads are selected from ones used in this technical field.

Though asphalt for asphalt paving is not limited, in cases where asphaltis used on the concrete base layer, asphalt suitable for the concretebase layer should be selected and improved asphalt is preferable. Themother asphalt mixture of half-flexible paving materials has 20-28% ofvacancy. Accordingly porous asphalt paving is available.

Special cement such as injection cement for half-flexible paving ispreferable as the cement can be hardened early. In addition sand isadded to the cement.

One example of the concrete paving comprises, in order on a roadbed, amacadam roadbed, an asphalt interlayer and a concrete layer. Theconstruction method is well known in the technical field of concretepaving. The overlay construction method in the present inventionincludes a method for used asphalt paving and a method for used concretepaving. Among the two methods, a great construction effect is availableespecially for the used concrete paving.

Generally, the concrete overlay method is used for recovering thesurface properties of the used concrete paving or strengthening thestructure thereof. Concretely, the concrete overlay method is carriedout by shaving the used concrete plate and then sticking-treatment,followed by constructing a determined thickness of new concrete bytapping.

According to the present invention, the surface layer of the newconcrete is obtained from 100 parts by weight of cement, 5-50 parts byweight of titanium oxide powder, 100-700 parts by weight of aggregateand 5-100 parts by weight of water. It is preferable to grind the shavedface of the used concrete paving with a method such as shotblast,followed by cleaning the ground face so as to reliably adhere the usedconcrete paving and the surface layer.

According to the present invention, a sheet for preventing a refractioncrack or a stress-relief layer or the like may be provided between thesurface layer and the concrete layer to decrease the refraction crack.The sheet and the stress-relief layer prevent the refraction crack aswell as have a cleaning action of the concrete layer attributable torainwater.

The types of adherence between the used concrete paving and the surfacelayer thereof comprise adhesion type, half-adhesion type, non-adhesiontype or the like. The adhesion type is preferable as the finishingheight is limited.

According to the present invention, the cement for the surface layer maybe conventional cement which includes normal Portland cement, high earlystrength Portland cement, super high early strength Portland cement,injection cement for half-flexible paving, moderate heat Portlandcement, white cement, Portland blast furnace slag cement, aluminacement, low heat cement, superfast-setting cement, etc. Among them, thewhite cement is preferable as the cleaning efficiency thereof is high.Additionally a center line formed by white cement has an NO_(x)-cleaningcapability as well as is excellent in easy recognition thereof.

Inorganic admixing additives such as pozzlan materials, Portland blastfurnace slag cement or the like as well as organic admixing additives oradditives ordinarily used in the technical field may be added to themixture for forming the surface layer used in the present invention ifnecessary. The pozzolan materials are added by 10-50 weight % relativeto cement.

The pozzolan materials or the pozzolan are compositions which are richin silicon dioxide and alumina having the property of reacting withcalcium hydroxide or calcium ion in the presence of water to generatenew hydrates and which include artificial pozzolan such as fly ash,blast furnace slag, silica fume, chaff ash or the like and naturalpozzolan originated in Siras white clay, volcanic ash.

The pozzolan reaction is a reaction which generates new hydrates frompozzolan and calcium hydroxides or calcium ion. Though the hydratesgenerated by the pozzolan reaction are substantially the same as inPortland cement, the reaction is apt to generate hydrates having a lowcalcium content. The pozzolan materials content less than 10% by weightrelative to cement is not sufficient to promote hardening , whereas thepozzolan materials content more than 50% by weight relative to cementlowers the cement content relatively by which initial strengthattainment becomes aggravated.

In addition, in the present invention, in cases where an admixingadditive for the surface layer is a blast furnace slag, the powder valueof the slag is preferably less than 4000 m²/g. The amount of the slagrelative to cement is 10-50% by weight which is the same as that of thesaid pozzolan materials.

In the present invention, the titanium oxide for the surface layer ispreferably a powder which is not surface-treated. The particle size ofthe powder is preferably fine and the specific surface of the same ispreferably more than 5 m²/g, more preferably 100-300 m²/g . In thepresent invention, any titanium oxide is preferable as the same isprovided with a cleaning action, anatase type is more preferably.

Titanium oxide showing 5-20% of weight loss comprising mainly moisturerelative to titanium oxide when the titanium oxide is calcined in therage of 150-800° C. is easy to be mixed with cement, more preferably8-15% of the weight loss.

Also, the kinds of titanium oxide are not limited, titanium monoxide andtitanium dioxide can be used individually or in a mixed combination. Inplace of these titanium oxides, metatitanic acid, orthotitanic acid orthe like which are intermediates can be used.

In the present invention, the amount of titanium oxide for forming thesurface layer, though depending on the types, particle sizes, etc.thereof, is 5-50 parts by weight of titanium oxide powder relative to100 parts by weight of cement, preferably 15-30 parts by weight oftitanium oxide powder and more preferably 10-40 parts by weight oftitanium oxide powder.

In cases where the amount of titanium oxide powder in the surface layerof the present invention is less than 5 parts by weight relative to 100parts by weight of cement, the NO_(x)-cleaning efficiency is inferior,whereas not only the anti-slip property is reduced but also the wearresistance is reduced in cases of exceeding 50 parts by weight.

In cases where the amount of aggregate is less than 100 parts by weightrelative to 100 parts by weight of cement, the anti-slip property andthe wear resistance are reduced, whereas in cases of exceeding 700 partsthe amount of titanium oxide is relatively reduced with the result ofimpairing the NO_(x)-cleaning efficiency. The composition of the surfacelayer of the present invention preferably comprises 10-50 parts byweight of titanium oxide powder, more preferably 20-50 parts , and50-300 parts by weight of aggregate, each relative to 100 parts byweight of cement.

Two kinds of coarse aggregate and fine aggregate can be used forpreparing the surface layer of the present invention. The coarse one ispreferably up to 20 mm ,and gravel and crashed stones may be used, forexamples. The preferable fine one is sand. In cases where glass grainsor silica sand having a high light-transmissivity are used as the sand,sufficient light can deeply penetrate from surface, thereby to providean enhanced NO_(x)-cleaning efficiency. The grain size of the sand ispreferably 1.2-5 mm.

The dough used for the surface layer of the present invention includes ahigh-performance reduction-water agent. The reduction-water agent may beconventional one. In cases of the high condensation products ofnaphthalenesulfonic acid, β-naphthalenesulfonic acid-formaldehydecondensation product or the like, for examples, may be used. In cases ofthe high condensation products of melaminesulfonic acid,melaminesulfonic acid-formaldehyde condensation product or the like, forexamples, may be used.

Furthermore, denatured lignin derivatives, creosote oils groupmaterials, polymers of alkylallylsulfonate or polycarboxyl acid groupmaterials one example of which is oxycarboxyl acid may be used.

Incidentally, fibers for preparing the surface layer of the presentinvention include vinylon fibers, carbon fibers, plastic fibers, steelfibers, etc. Among the fibers, plastic fibers and steel fibers arepreferable, and steel fibers are more preferable.

In the present invention, active carbon, zeolite, silica gel powder,Magadiite, petalite, etc. are used as adsorbing materials for thesurface layer. Among the adsorbing materials, active carbon is mostpreferable from the stand point of adsorbing effect. Zeolite is alsoconfirmed to have a high adsorbing effect and is preferable for thesurface layer. Any of natural and artificial zeolite can be used. Theamount of adsorbing materials which is 2-30%, more preferably 7-25% byweight relative to cement results in decomposing and removing NO_(x)during day by sunlight (ultraviolet rays included in the sunlight) underthe action of titanium oxide.

Furthermore, during night NO_(x) is adsorbed by the adsorbing materialsand during day the adsorbed NO_(x) is decomposed and removed byultraviolet rays. If the amount of adsorbing materials is less than 5%by weight, the adsorptive effect is not sufficient and the adsorption isimperfect during night having no sunshine.

On the other hand, if the amount of adsorbing materials is more than 30%by weight, it increases cost, and the relative amount of cement andtitanium oxide decreases with the result of decreasing strength andcleaning efficiency. Incidentally “% by weight” may be represented by“ratio relative to 100 weight parts by weight”.

Other additives which includes resin emulsion, re-emulsified powderresin, AE reagent or the like can be used to increase the fluidity andadhesiveness of the dough.

In cases where the paving layer is concrete paving or used concretepaving in overlay method in the present invention, the surface layerthickness is 1-300 mm, preferably 20-150 mm and more preferably 40-80mm.

In cases where the paving layer is asphalt paving (half-flexible paving)or used asphalt paving, the surface layer thickness is 2-15 mm,preferably 2-10 mm. The surface layer can be formed on the asphalt layercompletely or partially.

According the present invention, in cases where the surface layerthickness is more than 300 mm, sunlight is hard to penetrate and thetitanium oxide layer is useless. On the other hand, if the surface layerthickness is less than 1 mm, NO_(x)-cleaning efficiency is reduced anddurability is impaired.

According to the present invention, it is preferable that the surface ofpaving layer is provided with an unevenness. The unevenness may be anypatterns such as streaks, meshes, and embossed patterns. The strongadhesion between the paving layer and the surface layer is available bythe unevenness.

According to the present invention, embodiments of road paving comprisea paving layer which is asphalt paving or concrete paving and a surfacelayer containing cement and titanium oxide formed on the paving layer.In cases where the paving layer is composed of a part of used asphaltpaving, overlay method is adopted in such a manner that the repairedparts of the surface of the used asphalt paving are shaved to expose newsurfaces. Accordingly, after the new surfaces are exposed on the usedasphalt paving, surface layers which include cement and titanium oxideare formed on the new surfaces.

On the other hand, in cases where the paving layer is composed of a partof used concrete paving, concrete overlay method is adopted in such amanner that the repaired parts of the surface of the used concretepaving are shaved to expose new surfaces.

Accordingly, after the new surfaces are exposed on the used concretepaving, surface layers which include cement and titanium oxide areformed on the new surfaces.

According to the present invention, under the paving layer can be used abase layer which comprises concrete , rock bed or at least one selectedfrom soil, macadam and stone. Concretely, when the paving layer is anasphalt layer, the concrete base layer or the rock bed can be used asthe base layer, and also at least one selected from soil, macadam andstone can be used as the base layer.

Similarly, when the paving layer is a concrete paving, the concrete baselayer or the rock bed can be used as the base layer, and also at leastone selected from soil, macadam and stone can be used as the base layer.

The NO_(x)-cleaning paving structure of the present invention isespecially preferred to be formed near places where exhaust gas isdischarged from automobiles and concretely, can be formed on roadwaysand sideways. Accordingly, it is characterized that NO_(x) can becleaned immediately after the discharge of the exhaust gas by formingthe NO_(x)-cleaning paving structure on roadways and sideways. Incomparison with other construction materials used on the walls ofbuildings, the NO_(x)-cleaning paving structure of the present inventioncan efficiently clean NO_(x) to obtain a high NO_(x)-cleaning effect.

In the present invention, as the surface layer containing cement andtitanium oxide is formed on the asphalt layer, the asphalt layer is notdeteriorated by titanium oxide, and as the surface layer containscement, the durability thereof is excellent.

Particularly in cases where the asphalt layer is porous asphalt paving,a part of the surface layer penetrates into the pores of the porouspaving during construction with the result of strongly adhering thesurface layer and the asphalt layer and providing paving which has anincreased durability.

Furthermore in cases where the asphalt paving is one already used, theconstruction cost and the construction term are decreased as theconstruction of paving layer is only to change a part of the asphaltlayer.

Additionally the surface layer is strongly adhered by providing anunevenness to the surface of asphalt layer with the result of obtainingan excellent durability. Furthermore the good durability and stabilityof a road is available by using a concrete base layer. The surface layercontaining pozzolan materials can obtain an excellent strength as ahydrate is filled in voids. In cases where the surface layer containsadsorbing materials, an excellent NO_(x)-cleaning efficiency isavailable as NO_(x) is adsorbed during night and decomposed during dayby sunlight.

In the present invention, as the surface layer containing cement andtitanium oxide is formed on the concrete paving, the surface layer isprovided with NO_(x)-cleaning activity as well as the surface layer andthe concrete layer are strongly adhered each other as the materialsthereof are the same kind with the result that an excellent durabilityis available.

In addition, is cases where the concrete paving is used concrete paving,the surface of the paving is easily repaired as concrete overlay methodis used and also the surface on the used concrete paving can be providedwith NO_(x)-cleaning capability.

Accordingly, it is easy to construct paving which has NO_(x)-cleaningcapability as well as the cost and term of the construction can bedecreased.

EXAMPLES

A further detailed description is shown hereinafter by reference tospecific examples which are provided herein for purposes of illustrationonly and are not intended to be limiting unless otherwise specified.

Example 1

In FIG. 1, a 4-cm-thick interlayer (is not shown) and a 45-cm-thickconcrete layer 1 were formed on a particle size-controlled macadamroadbed, and a rubber-contained asphalt emulsion was spread on theconcrete layer as a tack coat and then a half-flexible paving material21 comprising a mother-asphalt mixture having a void volume of 23% waslaid and next roll-pressed by roller, thereby to form a paving layer 2.

After that, a slurry as a dough for surface layer was prepared byarranging and kneading a mixture comprising 240 parts by weight of sand,20 parts by weight of titanium oxide, 80 parts by weight of Portlandcement and 40 parts by weight of water. After the temperature of themother-asphalt mixture fell to a predetermined value, the slurry wasapplied to the surface of the paving layer, thereby to form a surfacelayer 3. A part of the slurry penetrated into the pores of the porousasphalt.

The thickness of the surface layer of paving structure formed in thisway was 8-10 mm. A high NO_(x)-cleaning effect was obtained in theabove-mentioned road paving due to the NO_(x)-cleaning action of thesurface layer 3.

In addition, the adhesion between the asphalt layer 21 and the surfacelayer 3 was satisfactory and an abrasion loss by labeling test was 0.4cm² which demonstrated the excellent durability of the paving.

Example 2

An ascon was prepared by mixing and heating 94 parts by weight ofparticle size-controlled macadam and 6 parts by weight of asphalt. Theascon was laid on a road and was roll-pressed by roller to form asphaltpaving. A slurry was prepared by mixing 70 parts by weight of Portlandcement,15 parts by weight of titanium dioxide, 70 parts by weight ofsand, 70 parts by weight of water and 0.1 parts by weight of Mighty-150(Trade mark). The slurry was spread on the asphalt layer, followed byleveling the same to form road paving. A high NO_(x)-cleaning effect wasobtained in the above-mentioned road paving due to the NO_(x)-cleaningaction of the surface layer.

In addition, the adhesion between the asphalt layer and the surfacelayer was satisfactory and paving excellent in durability was obtained.In addition, another road paving was prepared by replacing Portlandcement with white cement, which demonstrated that the road pavingreplaced with white cement had more excellent NO_(x)-cleaning abilitythan the road paving formed by using normal Portland cement.

Additionally, a center line was formed by using white cement, whichdemonstrated a higher NO_(x)-cleaning effect.

Example 3

An ascon was prepared by mixing and heating 94 parts by weight ofparticle size-controlled macadam and 6 parts by weight of asphalt. Asillustrated in a cross-sectional view of FIG. 2, a paving layer 2 wasprepared by laying the ascon on a particle size-controlled macadamroadbed 4 formed on a roadbed 5, followed by roll-pressing the same byroller to form an asphalt paving 21. The slurry of Example 2 containingtitanium dioxide was spread on the formed asphalt paving 21, followed byleveling the same to form road paving. The surface layer 3 of the roadpaving formed in this way demonstrated a high NO_(x)-cleaning effect dueto the NO_(x)-cleaning action. Also, in cases where stone was used for abase layer in place of the particle size-controlled macadam, the baselayer could be used, which demonstrated no unfavorable influence on theNO_(x)-cleaning action of the surface layer 3.

Example 4

A layer comprising a mother-asphalt mixture having a void volume of 23%was prepared and was roll-pressed by roller. Then a slurry was preparedby mixing 90 parts by weight of Hosoh-Acerade mark of injection materialfor half-flexible paving made by Mitubishi Materials Co.,super-rapidlyhardening type), 10 parts by weight of titanium oxide powder and 55parts by weight of water.

The slurry was spread on the asphalt layer, followed by leveling thesame to form road paving. The road paved in this way demonstrated thatthe excellent NO_(x)-cleaning effect of the present invention wasobtained due to the NO_(x)-cleaning action of the surface layer.

Example 5

Each paving structure was provided by adding fly ash or a blast furnaceslag as adsorbing materials to the composition of the surface layer ofthe asphalt paving structure for NO_(x)-cleaning of Example 1.

Each paving structure containing the above-mentioned pozzolan materialsdemonstrated a high strength.

Example 6

A paving structure was provided by adding active carbon as adsorbingmaterials to the composition of the surface layer of the asphalt pavingstructure for NO_(x)-cleaning of Example 1. The above-mentioned pavingstructure demonstrated an enhanced NO_(x)-cleaning efficiency.

Example 7

The concrete paved road in FIG. 3 is composed of an asphalt interlayer 7on a macadam roadbed 8, a used concrete paving 6 as a paving layer 2 onthe interlayer, and a surface layer 3 containing cement and titaniumoxide on the concrete paving.

First, a part of the surface of used concrete paving 6 in a concretepaved road was shaved, followed by abrasion-cleaning the shaved face byshotblast

A dough was prepared by mixing the composition listed in Table 1 and thesurface layer 3 was formed by covering the abrasion-cleaned face withthe dough in 5 cm thickness using a finisher for thin layer paving.After curing, pointing was carried out. Samples were cut off from theresulted paving and tested by the methods mentioned later. The resultobtained is shown in Table 1.

Example 8

A part of the surface of used concrete paving in a concrete paved roadwas shaved, followed by abrasion-cleaning the shaved face by shotblast.A dough was prepared by mixing the composition listed in Table 1 and theabrasion-cleaned face was covered in 7 cm thickness with the dough usinga finisher for thin layer paving. After curing, pointing was carriedout. Samples were cut off from the resulted paving and tested by themethods mentioned later. The result obtained is shown in Table 1.

Example 9

The surface of used asphalt paving in an asphalt paved road wasabrasion-cleaned by shotblast. A dough was prepared by mixing thecomposition listed in Table 1 and the abrasion-cleaned surface wascovered in 3 cm thickness with the dough using a finisher for thin layerpaving. After curing, pointing was carried out. Samples were cut offfrom the resulted paving and tested by the methods mentioned later. Theresult obtained is shown in Table 1.

NO_(x)-cleaning capability test

Test specimens each having an area of 10 cm×10 cm were cut off frompaving surfaces which had completely hardened. The test specimen wasground into 1 cm thickness, put into a glass container and theNO_(x)-cleaning capability thereof was tested.

The test method is as follows. The test specimen was put into a sealedglass container and an imitation gas having an NO_(x) concentration of 1ppm was introduced from the inlet of the container. The concentration ofthe gas flowing out of the outlet of the container was measured andNO_(x)-removal degree was calculated by the following formula.$\begin{matrix}{{{NO}_{x -}\quad {removal}\quad {degree}\quad (\%)} = {\frac{\begin{matrix}{{{NO}_{x}\quad {concentration}\quad {at}\quad {the}\quad {inlet}} -} \\{{NO}_{x}\quad {concentration}\quad {at}\quad {the}\quad {outlet}}\end{matrix}}{{NO}_{x}\quad {concentration}\quad {at}\quad {the}\quad {inlet}} \times 100}} & {{Formula}\quad 1}\end{matrix}$

TABLE 1 High early Reduction- NOx-cleaning Portland strength TitaniumFine Coarse water Steel capability Examples cement cement Water oxideaggregate aggregate agent fiber (%) 7 — 100 50 30 245 169 0.4 — 82 8 10048 30 247 206 0.4 — 85 9 — 100 50 30 245 169 0.4 30 87 (Unit: parts byweight) Titanium oxide: Crystal type - anataze, specific surface area -250 cm²/g Reduction-water agent: A high-performance reduction-wateragent, KAOH Mighty 150 Coarse aggregate: Particle size 5-20 mm

Application Available to Industry

The NO_(x)-cleaning paving structure of the present invention isprovided to roadways or sideways in areas where NO_(x) is found much.Specifically, concrete overlay method is applicable to used pavinglayers for providing the structure of the present invention and thepresent invention is used in paved roads construction such as repairingor strengthening surfaces thereof.

What is claimed:
 1. An NO_(x)-cleaning paving structure comprising: asurface layer disposed on an asphalt paving layer, wherein the surfacelayer is formed from a mixture comprising 100 parts by weight of cement,5-50 parts by weight of titanium oxide powder, 100-700 parts by weightof aggregate and 5-100 parts by weight of water.
 2. The NO_(x)-cleaningpaving structure of claim 1, wherein the asphalt paving layer comprisesused asphalt paving.
 3. The NO_(x)-cleaning paving structure of claim 1,wherein the surface layer has a thickness of 1-300 mm.
 4. TheNO_(x)-cleaning paving structure of claim 1, wherein the surface layerhas a thickness of 40-80 mm.
 5. The NO_(x)-cleaning paving structure ofclaim 1, wherein the mixture is in the form of a dough furthercomprising a high performance reduction water agent.
 6. TheNO_(x)-cleaning paving structure of claim 5, wherein the highperformance reduction water agent is selected from the group consistingof naphthalenesulfonic acid condensation products, β-naphthalenesulfonicacid-formaldehyde condensation products, melaminesulfonic acidcondensation products, melaminesulfonic acid-formaldehyde condensationproducts, denatured lignin derivatives, creosote oils, polymers ofalkylallylsulfonate, polymers of polycarboxylic acid, and mixturesthereof.
 7. The NO_(x)-cleaning paving structure of claim 1, wherein themixture further comprises 0.1-50 parts by weight of a fiber.
 8. TheNO_(x)-cleaning paving structure of claim 7, wherein the fiber isselected from the group consisting of vinylon fibers, carbon fibers,plastic fibers, steel fibers, and mixtures thereof.
 9. TheNO_(x)-cleaning paving structure of claim 1, further comprising aconcrete base layer disposed beneath the paving layer.
 10. TheNO_(x)-cleaning paving structure of claim 1, further comprising a rockbed base layer disposed beneath the paving layer.
 11. TheNO_(x)-cleaning paving structure of claim 1, further comprising a baselayer selected from the group consisting of soil, macadam, stone, andmixtures thereof disposed beneath the paving layer.
 12. TheNO_(x)-cleaning paving structure of claim 1, wherein the asphalt pavinglayer comprises porous asphalt paving.
 13. The NO_(x)-cleaning pavingstructure of claim 1, wherein the asphalt paving layer has an unevensurface.
 14. The NO_(x)-cleaning paving structure of claim 1, whereinthe mixture further comprises 10-50% by weight relative to the cement ofan admixing additive comprising pozzolan materials.
 15. TheNO_(x)-cleaning paving structure of claim 1, wherein the mixture furthercomprises 10-50% by weight relative to the cement of an admixingadditive comprising a blast furnace slag having a powder value less than4000 m²/g.
 16. The NO_(x)-cleaning paving structure of claim 1, whereinthe mixture further comprises 2-30% by weight relative to the cement ofan adsorbing material.
 17. The NO_(x)-cleaning paving structure of claim16, wherein the absorbing materials are selected from the groupconsisting of active carbon, natural zeolite, artificial zeolite, andmixtures thereof.